Tape measure having quick rewinding mechanism

Details Tape measure having quick rewinding mechanism Tape measure having quick rewinding mechanism

2001-04-09

2002-10-15

Jillions, John M. (Department: 3654)

Winding, tensioning, or guiding

Reeling device

With particular drive

C033S761000

Reexamination Certificate

active

06464160

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to measuring devices and particularly to a tape measure having a quick rewinding mechanism with improved characteristics.
BACKGROUND OF THE INVENTION
A conventional tape measure
1
is shown in
FIGS. 1
to
3
b
wherein a gear assembly
20
is provided in a hub, a first gear
21
is in a spindle in the hub, and a second driven gear
23
is on a lower cap thereof. The diameter of first gear
21
is larger than that of second driven gear
23
. Two opposed shafts
311
are provided with the idler gear set (i.e., idler gears
22
a
and
22
b
) sleeved thereon. Further, a smaller gear is meshed with first gear
21
while a larger gear is meshed with the second driven gear
23
. With the first gear
21
and second driven gear
23
rotated about the same axis and in meshing cooperation with idler gears
22
a
and
22
b
, a quick rewinding is carried out.
However, the previous design suffered from several disadvantages. For example, the idler gear (i.e., shaft
311
) tends to break thus malfunctioning the gear assembly. This is best illustrated in FIG.
1
. Further, the tape measure tends to vibrate irregularly, thus causing inconvenience to user. This is best illustrated in FIG.
2
. After analysis, it is found that the breaking of shafts
311
is caused by an excess force exerted thereon while performing a quick rewinding (see
FIG. 3
a
and
3
b
). In a clockwise rewinding of tape measure, force exerted on idler gear
22
a
by first gear
21
has a first component force along the X axis and a second component force along Y axis. In other words, a resultant force, generated along Z axis, is perpendicular to and exerted on shaft
311
(
FIG. 3
a
). Thus shaft
311
(i.e., idler gear
22
a
) tends to break after a long time of use while idler gear
22
b
is undamaged (FIG.
1
). In one consideration, the diameter of shaft
311
is increased in order to increase the durability of shaft
311
. However, this may adversely affect the strength of idler gears. In another consideration, the diameters of idler gears are also increased. However, this must significantly change the construction of the tape measure. Also, this will inevitably increase the size thereof. Thus, it is not practical. Moreover, first gear
21
is provided between two idler gears
22
a
and
22
b
and only supported by them. This is not a stable design as illustrated in FIG.
2
. Also, such drawback is not solved even when the diameters of shafts
311
(i.e., the rotation axes of idler gears
22
a
and
22
b
) are increased. Hence, further improvement is required.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a tape measure device having a quick rewinding mechanism comprising a gear assembly including a first drive gear, a second drive gear, and an idler gear set having a first, a second, a third, and a fourth idler gears each meshed with the first drive gear wherein the idler gears are equally spaced around the first drive gear. This can uniformly distribute a generated force to the idler gears while rewinding the tape measure device.


REFERENCES:
patent: 348805 (1886-09-01), Wheeler
patent: 1058311 (1913-04-01), Lewis et al.
patent: 1459454 (1923-06-01), Trotteer
patent: 1572001 (1926-02-01), Dotzert
patent: 2066779 (1937-01-01), Himmel
patent: 2168814 (1939-08-01), Willgoos
patent: 4813625 (1989-03-01), Takeda
patent: 5678452 (1997-10-01), Frazier
patent: 6134801 (2000-10-01), Miyasaka

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